Three-dimensional memory devices including self-aligned channel cap structures and methods for forming the same

A method of forming a semiconductor structure, comprising:

• forming a material layer over a carrier substrate;
• forming an alternating stack of insulating layers and spacer material layers over the material layer, wherein the spacer material layers are formed as, or are subsequently replaced with, electrically conductive layers;
• forming a memory opening through the alternating stack and into the material layer;
• forming an annular cavity around a bottom portion of the memory opening at a level of the material layer;
• forming a memory film on exposed surfaces of the memory opening and the annular cavity;
• forming an annular semiconductor structure within a remaining volume of the annular cavity;
• forming a semiconductor core structure on an inner sidewall of the annular semiconductor structure;
• and
• forming a vertical semiconductor channel on a top surface of the semiconductor core structure.